Among internal combustion engines, there is a type of using a feedback control system in which the air-fuel ratio of the air-fuel mixture fed to the engine proper is automatically controlled to a stoichiometric value by computing the informations given by an exhaust gas component sensor disposed in an exhaust conduit of the engine. In designing such a control system, accurate measurement of mass flow rate of air or fuel is very important. For this purpose, many kinds of mass flow measuring devices have been proposed, not one of these known devices, however, is perfect in measuring the mass flow rate with quick responsiveness.